Swinging bucket centrifuge rotors typically include a rotor head and a plurality of buckets. The buckets contain a sample to be centrifuged and are suspended from the rotor head. The buckets are supported by hangers which enable them to pivot about the mounting axes. When the rotor stops, the buckets hang vertically downward under the influence of gravity. When the rotor is spinning, the buckets swing outward in response to a centrifugal force. In a number of prior designs, an apparatus is incorporated into the rotor to limit the radial movement of the bucket, during centrifugation. Usually the radial movement is restrained by resting the bucket against a shoulder of the rotor head.
Swinging bucket rotors generally come in two designs: top-loaders and bottom-loaders. U.S. Pat. No. 4,190,195 to Chulay discloses a bottom-loading centrifuge rotor. The rotor has a plurality of evenly spaced cavities. The rotor is considered a bottom-loader because each cavity is not accessible from the top of the rotor head. A hanger member, which is spring biased in the radial direction toward the axis of rotation, is included in each cavity. Each hanger member is supported by a guide sleeve with the fastening means extending through it to prevent rotation of a bucket and hanger member. The bucket includes a flange portion proximate to the hanger member. The bucket is mounted so that the flange rests against the shoulder of the rotor, during centrifugation.
U.S. Pat. No. 4,400,166 to Chulay et al. discloses a top-loading centrifuge rotor. The rotor includes a rotor head and a plurality of evenly spaced cavities. Each cavity is cylindrical and extends through the rotor head, parallel to the spin axis, and includes two opposed grooves. The grooves extend from the top of the cavity and terminate proximate to the bottom of the cavity, forming a pocket to receive a hanger rod of a bucket. Each bucket is placed into the cavity from the top of the rotor, so that during centrifugation, a shoulder of the rotor head supports the flange portion of the bucket.
Each of the aforementioned designs has innate disadvantages. For example, the bottom loaders have the disadvantage that the operator cannot easily mount the buckets and may occasionally mount them incorrectly. As a result, during centrifugation the bucket may not pivot as intended and may become detached causing substantial damage to the sample, bucket and/or centrifuge. The top loading centrifuge requires the presence of large apertures bored through the rotor head. This results in a reduction in the number of buckets that may be suspended from the rotor head. In addition, neither of the aforementioned designs has a shoulder that is able to provide uniform support to the flange of a bucket. This substantially reduces the speeds at which a rotor may operate, as well as substantially reduce the rotor's operational life.
It is an object, therefore, of the present invention to provide an improved centrifuge rotor that is capable of operating at substantially higher speeds while maintaining a longer operational life than those disclosed in the prior art.
It is a further object of the present invention to provide a centrifuge rotor with an improved system by which to suspend the buckets that substantially reduces the likelihood of improperly mounting them onto the rotor.